| dc.description.abstract | The present paper is a short account of the state of the stock in recent
years of Squalus acanthias in European waters.
The basic material is the catch statistics from Bulletin Statistique
(ICES), the Norwegian spur-dog taggings, and certain catch/effort data
from the Norwegian long line fishery for spur-dog.
The fishery has expanded rapidly since the World War II and the
annual yield is now (1961) about six times higher than in 1945. The bulk
of the catch is shared between four countries: England, Scotland, France,
and Norway.
The main part of the yield originates from the waters around Shetland
(summer) and the Norwegian west coast (winter). Extensive taggings in
these localities show a free intermixing of the fish between these areas.
However, occasional recaptures from the same taggings are recorded from
the Barents Sea, Lofoten, the North Sea and Skagerak, the waters around
Ireland, the English Channel, and in the Bay of Biscay. It is, therefore,
possible that there exists only one stock common to the Northern and
Western Europe.
From a quantitative analysis of the tagging data it appears that the
estimate of the average total instantaneous mortality rate in the years
1960-1963 amounts to 0.72, and this high figure is interpreted as a
danger signal.
A certain measure of the catch per unit of effort was obtained from
various dealers by comparing the landings with the amount of bait used.
The series, comprising the years 1957-63, shows a heavily declining stock.
Using Shaeffer's model for stock assessment, the obtained series of
catch/effort, and the catch statistics froim Northern Europe, a maximum
equilibrium catch of about 50.000 tons is found. This level was, practically
speaking, reached in 1961.
The available data are not considered sufficient for a precise stock
assessment; but one important fact does emerge :The present exploitation
of the stock of Squalus acanthias in European waters is undoubtedly very
high. | |
